People who inject drugs (PWID) have been described as frequent users of health services such as emergency departments (EDs), however few studies have described demographic factors, patterns of substance use and previous health service use associated with frequent use of EDs in this population.Using a combination of self-reported data from a cohort of PWID and administrative ED data obtained through record linkage, we identified longitudinal factors associated with the use of ED services. Bivariate and multivariate analyses were conducted using negative binomial regression to identify exposures associated with both cumulative ED presentations, and logistic regression to identify exposures of frequent ED presentations (defined as three or more annual presentations).Among 612 PWID, over half (58%) presented to EDs at least once and over a third (36%) presented frequently between January 2008 and June 2013. Frequent and cumulative ED presentations were associated with reporting the main drug of choice as cannabis (AOR:1.42, 95%CI:1.07-1.89 and AIRR:2.96, 95%CI:1.44-6.07 respectively) or methamphetamine (AOR:1.62, 95%CI:1.17-2.2 and AIRR:2.42, 95%CI:1.08-5.46 respectively) compared to heroin, and past month use of mental health (AOR:1.42, 95%CI:1.08-1.85 and AIRR:3.32, 95%CI:1.69-6.53 respectively) and outpatient services (AOR:1.47, 95%CI: 1.00-2.16 and AIRR:0.95, 95%CI 1.52-10.28 respectively).PWID who are frequent users of EDs are likely to have complex health and substance use-related needs. EDs should actively refer people who present with cannabis and methamphetamine dependence to harm reduction services. Harm reduction services should ensure people referred from EDs are screened for co-occurring mental health conditions and receive adequate support.